Project Summary: The objective of this career development award is to continue to develop the academic career of Dr. Chun-An Chen, first as a postdoctoral researcher at The Ohio State University Heart and Lung Research Institute, with additional postdoctoral training and transition to an independent investigator in the field of cardiovascular research specializing in NOS function and redox signaling. Increased oxygen free radical generation, which can reduce the bioavailability of nitric oxide, is believed to be the primary pathogenesis of ischemia/reperfusion injuries. In the endothelium, endothelial nitric oxide synthase (eNOS) is the important enzyme that produces this critical molecule maintaining the cardiovascular function. Growing evidence suggests that increased oxidative stress alters the function of several enzymes through oxidative post-translational modifications, such as S-glutathionylation, nitration, or nitrosylation, all of which have been implicated in signal transduction. During the mentored phase, several questions will be addressed in Aim1 and Aim2: Aim1 is to determine the detailed mechanism of eNOS S-glutathionylation and thiol oxidation, as it pertains to cardiovascular diseases. Aim2 is to determine the role of Grx1 in the deglutathionylation process, redox regulation, and NOS function. The results gained from the mentored phase training will provide a bridge between mentored phase and independent phase. During the independent phase, Dr. Chen's research will focus on ex vivo mouse models regarding the effect of eNOS S-glutathionylation on vascular function, and the role of Grx1 on ischemia/reperfusion injury. Several mechanistic questions will be addressed with the following aims: Aim3 is to study the effect of eNOS Cys mutants on vascular function and resistance to oxidative modification during vascular dysfunction. Aim4 is to identify the role of Grx1 in ischemia/reperfusion injury, especially in the regulation of protein deglutathionylation and eNOS function, in mouse ex vivo heart models. By understanding the relationship between a redox regulatory enzyme (Grx) and NO production, this will provide a critical step toward understanding the mechanisms involved in the alteration of cardiovascular function during ischemia/reperfusion and oxidative stress. Successfully securing this K99/R00 award will foster Dr. Chun-An Chen's career research development and enable Dr. Chun-An Chen to become an independent investigator in the field of cardiovascular research.